RESUMO
The zebrafish (Danio rerio) has become a significant model for understanding the developmental regulation of gene expression and holds considerable potential for characterizing the development of the immune system. Using a number of different approaches, including heterologous hybridization and short-primer PCR, cDNAs for three different classes of light-chain genes were identified and characterized. The zebrafish light chains are similar to trout type 1, trout type 2, and catfish type F, respectively. T-cell antigen receptor alpha (TCRalpha) was also identified and characterized. A high proportion of unusual transcripts including sterile transcripts, germline VJC transcripts, aberrant splice forms, and V-V transcripts were encountered in the immunoglobulin and TCR cDNAs examined. The light-chain and TCRalpha loci each consist of multiple families of V gene segments, apparent even from the small numbers of cDNAs of each isotype sequenced. The gene sequences reported provide an essential set of markers of both B- and T-cell lineages that will facilitate investigations of immune system development.
Assuntos
Genes Codificadores da Cadeia alfa de Receptores de Linfócitos T , Regiões Constantes de Imunoglobulina/genética , Região de Junção de Imunoglobulinas/genética , Cadeias Leves de Imunoglobulina/genética , Região Variável de Imunoglobulina/genética , Peixe-Zebra/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , DNA Complementar , Regiões Constantes de Imunoglobulina/classificação , Isotipos de Imunoglobulinas/classificação , Isotipos de Imunoglobulinas/genética , Região de Junção de Imunoglobulinas/classificação , Cadeias Leves de Imunoglobulina/classificação , Região Variável de Imunoglobulina/classificação , Dados de Sequência Molecular , Filogenia , Homologia de Sequência de Aminoácidos , Peixe-Zebra/imunologiaRESUMO
This study was undertaken to determine whether a lack of VH domain diversity could explain, in part, the failure of Atlantic cod to respond to immunization with the production of specific antibodies. The variability of cod VH regions was studied in 113 cDNA and 2 genomic clones. A fourth VH family and a second putative JH element were identified. The expressed VH repertoire showed a clear bias in the pattern of VH family utilization, with about 80% of the clones belonging to the VH-III family. Furthermore, the VH-III family was complex and could be subdivided into several subfamilies, while little variation was seen within the other families. The VH family bias gives a somewhat reduced variability of the VH gene region of cod, but not lower than that of the rabbit IgM repertoire. The H chain CDR3 region of cod was longer than that of trout, frog and mouse, and also highly variable in sequence, probably reflecting a relative importance of this region in cod. On the other hand, the CDR3 length variability was restricted, and this may reduce the diversity of the cod VH region.
